This invention relates to a current-collecting elastic tire for a vehicle, and contemplates the provision of a tire of the kind above described in which electrodes are embedded in the tread portion of the tire body to be exposed at one end thereof from the tire tread surface and electrically connected at the other end thereof to the vehicle by electrical wiring. Further the present invention contemplates the provision of a tire of the above character, which collects current while making rolling movement and has a longer service life than that of prior art current collectors of the type adapted for collecting current by frictional sliding engagement due to the fact that less friction is encountered during collection of current.
Vehicles driven by electric power, for example, electric cars, trolley buses, subway cars, etc. collect current from an associated exclusive power supply line by a special current collector such as a pantograph. Vehicles relatively recently developed as transportation means in a city traffic system, such as monorail cars and PRT cars (Personal Rapid Transit System) which run on a track laid exclusively therefor, and provided with auxiliary guide wheels besides the main wheels which support the load of the vehicle body. When these vehicles are driven by electric power, a current collecting means of a form similar to the previous combination of a power supply line and a pantograph is still employed therein.
A vehicle guiding equipment is provided exclusively for the vehicles used as the transportation means in such a city traffic system. Therefore, utilization of this vehicle guiding equipment as a path of electric power supplied to the vehicles can greatly reduce the required materials and costs. However, mere utilization of this vehicle guiding equipment as a path for electric power supply cannot in any way attain a remarkable progress over the prior art technique inasmuch as a special current collector of the kind similar to the prior art one is employed still to collect current from such a power supply path. It is therefore desirable that the tire itself of the guide wheel serves also as a current collector, but no tire capable of collecting current has been proposed hitherto. A wheel of good electrical conductor or a metal wheel may be employed as this guide wheel, but such wheel is defective in that it is devoid of the high elasticity of rubber tires.
Further, a conventional tire is an electrical insulator in itself due to the fact that it is composed essentially of tire cords reinforcing the tire structure and a mass of rubber for protecting the tire cords. Electrodes may be embedded in such a tire so that the tire can collect current. A method previously commonly employed for forming a rubber tire comprises bonding together on a cylindrical tire molding drum a plurality of carcass members formed by covering the tire reinforcing layers of tire cords with rubber, bonding layers of rubbers for forming the tread and side cover layers of the tire, and placing the cylindrical semi-finished unvulcanized tire in a vulcanizing press to shape the unvulcanized tire in a form of a solid torus and to vulcanize the unvulcanized tire for obtaining a predetermined tire configuration. Thus, according to the prior art method, it has been a matter of extreme difficulty to accurately embed desired electrodes and electrical wiring (power supply conductors) in predetermined positions. Such difficulty may be overcome by previously embedding electrical wiring within the tire walls and driving metal pieces analogous to ice spikes into the vulcanized tire to provide the desired electrodes. However, another difficulty arises in respect to the manner of electrical connection between the electrodes and the electrical wiring, and an additional problem arises with respect to the mechanical strength, etc. of the tire since these electrodes are not previously disposed in the tire during molding but are mechanically driven into the shaped tire.
A technique of making a tire by casting an elastomer in liquid state has been recently developed. This cast tire is made by pouring an elastomer in liquid state into a space of tire configuration defined between a tire mold forming the external shape of the tire and an internal mold forming the internal shape of the tire, and curing the elastomer to obtain the desired tire. When, for example, polyurethane rubber is used as this elastomer, the molded article thus obtained has a high tensile strength, a great resistance to wear and a high rigidity compared with conventional molded articles of rubber. Therefore, it has become able to obtain a tire which can sufficiently withstand servere uses without requiring any reinforcing members or tire cords commonly employed in prior art tires. The development of this unique cast tire technique has enabled to easily obtain a tire having electrodes and electrical wiring embedded therein.